For example, Patent document 1 discloses a collision object discriminating apparatus as a conventional pedestrian collision detection apparatus for detecting collision between a vehicle and a pedestrian.
The collision object discriminating apparatus includes an optical fiber sensor, two acceleration sensors, and a collision object discriminating ECU. The optical fiber sensor is provided for a front bumper. The acceleration sensors are provided on the tops of left and right front side members. The collision object discriminating ECU compares a detection result from the optical fiber sensor with an optical fiber sensor threshold Mth. The collision object discriminating ECU also compares a detection result from the acceleration sensor with an acceleration sensor threshold Gth2. The collision object is determined to be a pedestrian when (i) the detection result from the optical fiber sensor is greater than or equal to the optical fiber sensor threshold Mth and (ii) the detection result from the acceleration sensor is smaller than the acceleration sensor threshold Gth2.                Patent Document 1: JP-2006-142876 A (corresponding to US2006/0103514)        
When the collision object is determined to be a pedestrian, there is a specific correlation between a detection result from the optical fiber sensor and a detection result from the acceleration sensor. The above-mentioned collision object discriminating apparatus compares detection results from the optical fiber sensor and the acceleration sensor with independent thresholds to determine whether or not the collision object is a pedestrian. This cannot fully use the correlation between a detection result from the optical fiber sensor and the detection result from the acceleration sensor. The collision object may be determined to be a pedestrian contrary to fact. Inversely, the collision object may not be determined to be a pedestrian contrary to fact. It has been difficult to improve the accuracy for determining a pedestrian.